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Question Bank [ 2022 ] — Physics STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsQuestion Bank [ 2022 ]3 Marks
Question
Explain given cases related to energy transfer between the system and surrounding –
  1. energy transferred $(Q) > 0$
  2. energy transferred $(Q) < 0$
  3. energy transferred $(Q) = 0$
✓

Answer

Consider a system with temperature $T_S$​​​​​​​ is kept in an environment of temperature $T_E$​​​​​​​. Let $Q$ be the energy transferred between the system and the environment.
  1. When the temperature of the system is less than that of the environment $(T_S < T_E)$, the energy flows into the system as shown in figure (a).
    Image
    As a result, the system gains energy and $Q$ is positive.
  2. When $T_S > T_E$​​​​​​​, the system loses energy i.e., the energy flows from the system into the environment as shown in figure (b).
    Image
    In this case, $Q$ is negative.
  3. For $T_S = T_E​​​​​​​$​​​​​​​, as shown in figure (c), the system and the environment are in thermal equilibrium and there is no transfer of energy i.e., $Q = 0.$
    Image

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